Device for retention of ink jet nozzle clogging and ink spraying

ABSTRACT

A device for use in an ink jet printing system which comprises a vapor chamber and means for moving said chamber to enclose the jet nozzles during shut-down period to prevent ink from drying at the nozzle. A sharp edge wall is provided to keep the charging electrodes and deflection plates free from ink spraying at pressure shut-off and means are provided for mounting the charging electrodes for movement out of the jet path prior to shutdown of the printer to prevent ink spraying thereon at pressure shut-off.

United States Patent n91 Chen et al.

[ 1 Oct. 1,1974

[ DEVICE FOR RETENTION OF INK JET NOZZLE CLOGGING AND INK SPRAYING {75]Inventors: Winston II. Chen; Johann H. Meier;

Walter T. Pimbley, all of Vestal, NY.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: June 27, 1973 [21] Appl. No.: 374,224

[52] US. Cl. 346/75, 346/140 [51] Int. Cl. ..G01d 15/18 [58] Field ofSearch 346/75, 140

[56] References Cited UNITED STATES PATENTS 1,967,900 7 1934 Perry etal. 346/l40 X 3,039,438 6/1962 Brown 346/140 3,346,869 l0/l967 3,6l8,858ll/l97l 3,737,914 6/l973 Stone 346/75 Culp Hertz 346/75 PrimaryExaminer,loseph W. l-lartary Attorney, Agent, or FirmGerald R. Gugger 57 1 ABSTRACT 5 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION orink is caused to issue from a nozzle in the form of a succession of tinyindividual droplets which are directed toward the surface of a recordmember. As the individual droplets are formed, they are given anelectrostatic charge which is a function of the instantaneous value ofan input signal which is to be recorded. The charged droplets are causedto pass between a pair of electrostatic deflection plates. Constant highvoltage charges are applied to the deflection plates to produce aconstant high voltage electric field between adjacent plates. As thecharged droplets pass through the electric field, they are deflectedfrom their normal path by an amount which is a function of the magnitudeof the charge on each of the droplets and in a direction which is afunction of the polarity of the charge on the individual droplets. Eachdroplet of the ink or writing fluid has its own unique chargecharacteristic for directing it to the desired print position on therecord member.

In a printing system of the type described above, nozzle clogging haspresented a well known problem. One of the reasons of clogging is due tothe ink drying in the nozzle over a standstill period, such as theweekend. The nozzles have an inside diameter in the order of 0.001 or0.002 of an inch and ink allowed to stand therein tends to clog theopening when the ink has dried. Prior attempts have been made to solvethis problem. For example, the aforementioned US. Pat. No. 3,596,275discloses a system for removing the residual ink from the nozzle byflushing it out with a suitable solvent such as water. A reservoir isprovided which contains rinse water and a pressure source is connectedto the reservoir to establish a suitable pressure head. Another systemis disclosed in US. Pat. No. 3,346,869 wherein a solenoid-operatedsilicone-coated pad is brought up to close the nozzle opening to preventthe ink from drying. Both these systems are relatively expensive andcomplex to operate.

Another problem which exists is that of ink spraying. When the jetpressure is turned off to shut down the printer, the residual pressurein the ink supply line usually causes irregular sideway spraying thatwets and messes up the charging electrodes and the deflection plates.From practical experience, it is known that it is imperative to keep theelectrodes and deflection plates dry lest arcing and short circuitsoccur and cause machine breakdown. Therefore, every time before theprinter is turned on, it is necessary to dry up the ink mess on theelectrodes and deflection plates left by the ink spraying of the lastshutdown. This is an extremely cumbersome and time-consuming taskbecause there are generally 66 charging electrodes and 67 deflectionplates in a line printer and they are of small dimensions with a tinyspace in-between.

In view of the above, it was considered desirable to devise an improveddevice which would not only prevent nozzle clo'gging but which alsowould keep the electrodes and deflection plates free from ink spraying.

SUMMARY OF THE INVENTION In one preferred embodiment of the presentinvention a support member is provided on which is mounted the row ofcharging electrodes. This support member is fastenedto another memberhaving a hollow chamber portion with an opening or mouth in alignmentwith the electrodes and spaced therefrom. The chamber is partiallyfilled with ink or water with a chemical additive such that a high vaporpressure is maintained in the remaining portion of the chamber. Theelectrode and chamber assembly is movably mounted and transducer means,such as a solenoid, is provided to move the assembly.

A row of ink jet nozzles is fixedly mounted and when the electrode andchamber assembly is positioned for a printing operation, the row ofcharging electrodes is positioned in alignment with the row of nozzlesso that the ink droplets are directed between the electrodes and theopening in the chamber is spaced away from the nozzles. When the printeris shut down and prior to turning off the pressurized ink, thetransducer is activiated to move the electrode and chamber assembly sothat the row of charging electrodes is moved out of the discharge pathof the nozzles and the chamber is moved so that itsmouth will interceptthe nozzles and the jet stream, after which the ink pressure is turnedoff. Thus, ink spray is prevented from reaching the electrodes and thedeflection plates mounted in alignment with the electrodes and also thenozzles which are now enclosed in the mouth of the vapor chamber arekept damp enough to prevent ink drying and clogging. A sharp edged sidewall is also provided on the assembly against which the mouth of thechamber moves, said wall serving to contain the vapor in the chamber andalso to further prevent the ink spray from reaching the electrodes andthe deflection plates.

In another embodiment of the invention, the charging electrodes aremounted on a movable support along with a trough containing water orwater and a detergent. Activation of a transducer will move theelectrodes out of the discharge path of the nozzles and the trough willmove into position to intercept the nozzles with the nozzle tipsextending below the water line.

In still another embodiment of the present invention, the print head orrow of ink jet nozzles is rotatably mounted and transducer means isprovided to rotate the nozzles away from the electrodes and into atrough containing water or water and a detergent.

The present invention advantageously solves the aforementioned problemsof nozzle clogging and ink spraying by making use of arrangements whichare simple, reliable and inexpensive.

It is, then, a primary object of the present invention to provide anovel and improved arrangement for preventing nozzle clogging and inkspraying when an ink jet printing system is shut down.

A further object of the present invention is to provide in an ink jetprinting system means for enclosing the ink jet nozzles in a vaporchamber when the system is shut down.

A still further object of the present invention is to provide in an inkjet printing system means for moving the charging electrodes out of thedischarge path of the ink jet nozzles when the system is to be shutdown.

Another object of the present invention is to provide a novel andimproved. arrangement for printing nozzle clogging and ink spraying whenan ink jet printing system is shut down which comprises a movableassembly having a row of charging electrodes and a vapor chamber.

A further object of the present invention is to provide an ink printingsystem means for submerging the inkjet nozzles in a liquid when thesystem is shut down.

Another object of the present invention is to provide a novel andimproved arrangement for preventing nozzle clogging and ink sprayingwhen an ink jet printing system is shut down which comprises a movableassembly having a row of charging electrodes and a container of liquid.

A still further object of the present invention is to provide in an inkjet printing system means for moving the ink jet nozzles away from thecharging electrodes and into a container of liquid.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention as illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of aportion of an ink jet printing system shown in printing position andincluding the embodiment of the vapor chamber of the present invention.

FIG. 2 is an isometric view of the ink jet printing system of FIG. 1shown in non-printing position with the vapor chamber in position toprevent nozzle clogging.

FIG. 3 is a schematic diagram of an ink jet printing system shown inprinting position and including the embodiment of the movable liquidcontainer of the present invention.

FIG. 4 is a schematic diagram of the ink jet printing system of FIG. 3shown in non-printing position with the liquid container in position toprevent nozzle cloggmg.

FIG. 5 is a schematic diagram of an ink jet printing system shown inprinting position and including the embodiment of the liquid containerand the movable print head of the present invention.

FIG. 6 is a schematic diagram of the ink jet printing system of FIG. 5shown in non-printing position with the print head in position toprevent nozzle clogging.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1 there ispartially shown the previously described ink jet printing system whichexemplifies one type of system for which the present invention isadapted for use. A support bracket 10 is provided which has a row ofspring blade support tabs 11 and fastened to each tab is a support block13 and a piezoelectric transducer 14. Running through each block andtransducer assembly is an ink pipe 15 having a nozzle 16 and each inkpipe is connected by way of a tubing 17 to a suitable source of inkunder pressure. The transducers 14, which may be excited by a suitablesinusoidal oscillator, are used to introduce varicosities in the jetstreams by vibrating the nozzle 16 at the desired frequency to produce asuccession of ink droplets 18 which are substantially uniform indimension and frequency.

Each droplet stream 18 passes through a U-shaped charging electrode 19with the row of electrodes being fastened to a U-shaped support member20 via the contact pins 21. The electrodes 19 are used to variablycharge the individual ink droplets in accordance with input datainformation. From the charging electrodes, each stream of dropletspasses between a pair of deflection plates 22 with the row of deflectionplates mounted on a support bracket 23. The deflection plates areoppositely charged to a constant voltage and they deflect the chargeddroplets onto the record medium to effect printing. Not all of the inkdroplets will be charged and those that are not are deflected into asuitable gutter 24 to be returned back to the supply.

In accordance with the present invention, means are provided forpreventing ink from drying at the nozzles during printer shutdown and tokeep the charging electrodes and deflection plates free from inkspraying at pressure shut off. In the present embodiment, this isaccomplished by slideably mounting the charging electrode support member20 on a pair of end rods 25 mounted in a pair of end brackets 26.Attached to the bottom of the support member 20 by suitable screws (notshown) is a vapor chamber 27 with an opening 28 having a partiallyclosed lip portion 29. The chamber is partially filled with avapor-forming liquid 30 such as water with a chemical additive or inkwhich will produce a mist or vapor 31 in the remaining upper portion ofthe chamber. If desired, the chamber may be provided with a suitabledrain hose at the bottom. Connected to the side of the chamber by way ofa bracket 32 is the shaft of a solenoid 33 mounted in a support bracket34. As the system is shown in FIG. 1, the solenoid has been activated tomove the support member 20, the charging electrodes 19, and the vaporchamber 27 downward into a printing position. In this position, the rowof charging electrodes is in alignment with the row of nozzles toreceive the droplet streams and the mouth or opening 28 of the vacuumchamber is down and away from the nozzles.

Referring now to FIG. 2, when shutting down the printer system andbefore the ink pressure is turned off, solenoid 33 is released and acoil spring 35 mounted on each of the end slide rods 25 will move thesupport member 20, the charging electrodes, and the vacuum chamberupward to a non-print position. Instead of the springs, a double-actingsolenoid could be used to move the assembly both up and down. In thisnon-print position, it can be seen that the charging electrodes 19 aremoved up out of the path of the jet streams and the vapor chamber ismoved up so that the opening 28 encloses the nozzles and intercepts thejetstreams. The ink pressure can now be shut-off. The partially closedlip portion 29 protects the charging electrodes and the deflectionplates from ink spraying due to residual ink in the nozzles. Also, thevapor pressure in the chamber, either with or without temperaturecontrol, will keep the nozzles enclosed in the chamber damp enough toprevent ink drying and clogging during the shutdown period. To furtherenhance the containment of the vapor and the protection of the platesand electrodes, a sharp edged wall or bar 36 may be fastened to supportbracket 10 so that the lip portion 29 will abut against it in thenon-print position. Before start-up ink may be forced through thenozzles and into the vapor chamber to expell any air that might be inthe nozzles.

A second embodiment of the present invention is shown in FIGS. 3 and 4.Referring to FIG. 3, there is shown, schematically, a print head 37, aplurality of ink jet nozzles 38, a plurality of charging electrodes 39,a plurality of deflection plates 40, an ink gutter 41, and the recordmedium 42. The charging electrodes are mounted in a suitable movablemember 43 and also mounted on the member is a partially open container44 which is filled with a liquid 45, such as water or water with adetergent. The movable member 43 is connected to a suitable transduceror double acting solenoid 46. As shown in FIG. 3, the system is in aprinting position. Referring now to FIG. 4, when shutting the systemdown, solenoid 46 is activated to move member 43 so that the chargingelectrodes are out of the path of the jet streams and the container 44is positioned to intercept the nozzles with the nozzle tips submergedbelow the water line. Thus, with the nozzles submerged in water, nozzleclogging is prevented during shutdown of the system. Before start-up,ink could be forced through the nozzles into the water container toexpel any water that had entered the nozzles.

A third embodiment of the present invention is shown schematicallyinFlGS. and 6. Referring to FIG. 5, the system comprises a print head47, a plurality of ink jet nozzles 48, a plurality of chargingelectrodes 49, a plurality of deflection plates 50, an ink gutter 51,and the record medium 52. The print head is fixed on a rotatable shaft53 and fastened on the end of the shaft is a hand knob 54. Positionedbelow the nozzles is an open container 55 which is filled with a liquid56, such as water or water with a detergent. As shown in FIG. 5, thenozzles have been rotated upward into a printing position. Referring toF IG. 6, when shutting down the nozzles are rotated downward so that thenozzle tips are submerged below the water line in the container toprevent clogging.

The above embodiments of the invention have been applied to oneparticular type of multiple nozzle printing system, however, they willwork equally as well for other types of multiple nozzle systems and alsofor singie nozzle on demand types of printing systems.

While the invention has been particulary shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. In an ink jet printing system having nozzles for discharging inkdroplets, charging electrodes for charging said droplets, and deflectionplates for deflecting the charged droplets onto a record medium, theimprovement comprising:

means for subjecting said nozzles to a vapor atmosphere when said systemis shut down to prevent clogging of the nozzles by dried ink.

2. An ink jet printing system comprising:

a row of ink jet nozzles for discharging ink droplets to carry out aprinting operation;

a row of charging electrodes for charging said droplets;

a row of deflection plates for deflecting said charged droplets onto arecord medium;

a movable support member on which said row of charging electrodes ismounted;

a vapor chamber mounted on said support member and having an opening;

means for creating a vapor in said chamber;

means for moving said support member into a printing position whereinsaid row of electrodes is positioned between said nozzles and deflectionplates and in the droplet discharge path of said nozzles, and theopening in said vapor chamber is positioned away from said nozzles; and

means for moving said support member to a nonprinting position whereinsaid row of electrodes is positioned out of the droplet discharge pathand said row of nozzles is enclosed in the opening in said vapor chamberto prevent clogging of the n0zzles by dried ink when the system is shutdown.

3. An ink jet printing system as set forth in claim 2 wherein said vaporchamber opening has a partially closed lip portion to contain said vaporand to shield said electrodes and deflection plates from being sprayedby residual ink in the nozzles.

4. An ink jet printing system as set forth in claim 3 and including awallagainst which the partially closed lip portion of said containerabuts when the system is in the non-printing position.

5. An ink jet printing system comprising:

a row of ink jet nozzles for discharging ink droplets to carry out aprinting operation;

a row of charging electrodes for charging said droplets;

a row of deflection plates for deflecting said charged droplets onto arecord medium;

a movable support member on which said row of charging electrodes ismounted;

an open container mounted on said support member;

a supply of liquid in said container;

means for moving said support member into a printing position whereinsaid row of electrodes is positioned between said nozzles and deflectionplates and in the droplet discharge path of said nozzles and saidcontainer is positioned away from said nozzles; and

means for moving said support member to a nonprinting position whereinsaid row of electrodes is positioned out of the droplet discharge pathand said row of nozzles have their tips submerged in the liquid in saidcontainer to prevent clogging of the nozzles by dried ink when thesystem is shut down.

Pww UNITED: STATES PATENT. OFFICE 'CERTIFXCATE OF CORRECTION Patent o3,839,721 7 Dated October 1, 197a Inventofls) wlnston H Chen et al v Itis certified that error app'ears in the above-identified patent and thatsaid Letters Patent are. hereby fcorrected as shown below:

In the title "RETENTIbN" should read --PREVENTION-.

Signed and sealed this 7th day of January 1975.

(SEAL) I 1 K e v t,;

" Attest v I cCoy-M;GIBSON JR; t C.-,-MARSHALL DANN L Attesfcing-Officer 3 Commissioner of Patents UNITED: STATES PATENT, OFFICE po-mosn(5N1!) I '(IERTIFICATE OF C(DRREQTIQN Patent No. 3,839,721 Date October1', 197a Inventor) Winston H. Chen et el It is certified that errorappears in the above-identified patent and that said Letters Patent are.hereby corrected as shown below:

In' the title "RETENTION" should read --PREVENTION. 1

Inthe-abstract,-line-S, .edq ould r d -r- Signed and sealed: this 7thday of January 1975.

' (SEAL) V Attest: v

' MCCOY MQ-GIBSON JR.- C.-MAR SHALL DANN v Attesting OfficerComissiorier' of Patents"

1. In an ink jet printing system having nozzles for discharging inkdroplets, charging electrodes for charging said droplets, and deflectionplates for deflecting the charged droplets onto a record medium, theimprovement comprising: means for subjecting said nozzles to a vaporatmosphere when said system is shut down to prevent clogging of thenozzles by dried ink.
 2. An ink jet printing system comprising: a row ofink jet nozzles for discharging ink droplets to carry out a printingoperation; a row of charging electrodes for charging said droplets; arow of deflection plates for deflecting said charged droplets onto arecord medium; a movable support member on which said row of chargingelectrodes is mounted; a vapor chamber mounted on said support memberand having an opening; means for creating a vapor in said chamber; meansfor moving said support member into a printing position wherein said rowof electrodes is positioned between said nozzles and deflection platesand in the droplet discharge path of said nozzles, and the opening insaid vapor chamber is positioned away from said nozzles; and means formoving said support member to a non-printing position wherein said rowof electrodes is positioned out of the droplet discharge path and saidrow of nozzles is enclosed in the opening in said vapor chamber toprevent clogging of the nozzles by dried ink when the system is shutdown.
 3. An ink jet printing system as set forth in claim 2 wherein saidvapor chamber opening has a partially closed lip portion to contain saidvapor and to shield said electrodes and deflection plates from beingsprayed by residual ink in the nozzles.
 4. An ink jet printing system asset forth in claim 3 and including a wall against which the partiallyclosed lip portion of said container abuts when the system is in thenon-printing position.
 5. An ink jet printing system comprising: a rowof ink jet nozzles for discharging ink droplets to carry out a printingoperation; a row of charging electrodes for charging said droplets; arow of deflection plates for deflecting said charged droplets onto arecord medium; a movable support member on which said row of chargingelectrodes is mounted; an open container mounted on said support member;a supply of liquid in said container; means for moving said supportmember into a printing position wherein said row of electrodes ispositioned between said nozzles and deflection plates and in the dropletdischarge path of said nozzles and said container is positioned awayfrom said nozzles; and means for moving said support member to anon-printing position wherein said row of electrodes is positioned outof the droplet discharge path and said row of nozzles have their tipssubmerged in the liquid in said container to prevent clogging of thenozzles by dried ink when the system is shut down.